Corner key for window component assembly

ABSTRACT

The present invention relates to corner keys used in assembling structural components to form various structural shapes, such as a frame and sash section for a window, door panel, or other building or architectural construction. The structural members are formed by a process that includes continuously roll-forming a first sub-part and a second sub-part from pre-treated metal in flat coil-stock form. A thin layer of Extrudable Thermal plastic (ETP) is then selectively extruded to both the outside and inside surfaces of the sub-parts. Some of the ETP is extruded onto the roll-formed sub-parts in a functional shape, such as a &#34;C&#34; shaped pocket used to clip parts together. The sub-parts are joined together to form structural component material that can then be cut and fabricated to form individual structural components. Once the roll-formed structural components are selectively joined or coupled together to form a frame or sash, a shot of urethane foam is injected into the frame or sash and allowed to expand to fill the interior of the frame or sash. The addition of the foam provides permanent adhesion among the various structural components and significantly improves the structural integrity of the window casement. Hollow corner keys, the subject of the present invention, can be further added to improve the structural integrity of the window casement.

RELATED APPLICATION

This is a divisional application of Application Ser. No. 09/148,516,filed Sep. 4, 1998, now pending.

BACKGROUND OF THE INVENTION

This invention relates broadly to structural components, such as studsused for structural framing of building systems, i.e., beam columns,etc., and particularly to casement sections, or frames and sashes forwindows, doors, panels or other building or architectural constructions.For convenience herein, the invention will be defined and described withparticular reference to window casements (frames and sashes), but itwill be understood that the invention is of general utility.

Existing window casement components used in the construction of windowframes and sashes suffer from a number of disadvantages and it isdifficult to meet all the practical requirements without excessiveweight or cost. For example a window casement must have adequatestrength, the corners and other joints must be rigid, the casementmembers must have longitudinal and torsional rigidity, the members mustbe durable, resistant to impact and damage, corrosion resistant,leakproof, remain stable at temperatures above 150° F., and alsopreferably should have thermal insulating properties to preventexcessive conduction of heat from the internal to the external surfaces,or vice-versa.

Traditional timber and extruded aluminum and polyvinyl chloride (PVC)and other composite material members fail to meet a number of theserequirements, while conventional solid or hollow extruded aluminum orpultruded glass resin shapes are expensive and also fail to meet many ofthe requirements. Window casement components have also been constructedin hollow rolled aluminum brass or steel sections, which may be coatedto resist corrosion, but in order to provide adequate longitudinal andtorsional strength the gauge of the rolled sheet must be quitesubstantial, which results in a heavy and expensive construction.Moreover, it is difficult to form corner and other joints since steelcomponents coated with material such as synthetic plastics orpultrusions cannot be welded without damaging the coating.

Various other composite constructions have been proposed but all knownconstructions are either expensive or fail to meet the optimum designrequirements.

Prior art conventional PVC frames are a faulty combination of lowrigidity with poor material shear strength that requires an aluminum orsteel stiffener be placed into one of the internal cavities to enhanceits structural properties. The rigidity enhancement necessary isminimized by locating the structural member close to the neutral axis ofthe PVC shape.

Additional mechanical problems with the conventional PVC design includeexcessive thermal expansion with temperature fluctuations from winter tosummer and extreme temperature gradients from the environmentallycontrolled inside of the building to the natural environment of theoutside of the building, where a typical window will expand and contract1/4 inch in height and width. This places stress on the welded cornerjoints and nailing fin which has proven to cause fracturing failures inthe field. Additionally, the PVC shape is generally restricted tolighter colors such as white and beige, as darker colors can allow thePVC temperatures to rise above the heat deflection temperature of thematerial, which is approximately 140°-150° F.

SUMMARY OF THE INVENTION

The present invention relates to corner keys used in assemblingstructural components to form a structural shape, such as a frame andsash section for a window, door panel, or other building orarchitectural construction. The structural components are formed by aprocess that includes continuously roll-forming structural componentsfrom pre-treated metal in flat coil stock form. A thin layer ofExtrudable Thermal Plastic (ETP) is then selectively extruded to boththe outside and inside surfaces of the roll-formed component. Some ofthe ETP is extruded onto the roll-formed component in a functionalshape, such as a "C" shaped pocket used to clip parts together.

This process of extruding ETP shapes over roll-form members extends thetraditional roll-forming process with the capability of incorporatingadditional functional shapes into the roll-formed component that eithercould not be done by roll-forming alone or would be cost prohibitivefrom a roll-form tooling standpoint. The process has the advantage ofbeing completed four to eight times faster than traditional extruded ETPmembers. This, combined with utilizing thin roll-formed metal profilesand ETP materials allows this process to produce structural componentsthat are approximately the same manufacturing cost of traditionalextruded components, while incorporating superior mechanical properties.

After the roll-formed/extruded components leave the extruder, they arecut into lineals and are ready to be fabricated into frame componentsused in the window and/or structural shape assembly. With specificreference to window casement frames, the lineals are miter-cut to formframe components which are joined or coupled together byinjection-molded corner keys to form a window casement frame. The cornerkeys are the subject of the present invention. Next, a one to ten poundshot of urethane foam is injected into the window casement frame andallowed to expand to fill the interior of the frame. The hollow cornerkeys are designed to allow the liquid foam to pass through with minimalrestriction. In addition, the keys have holes strategically molded intotheir outer walls to allow foam to flow around the outside of the cornerkey, which locks the key to the frame or sash components. A series ofrecesses, which are integrated into the injection-molded corner key,allow the foam to flow freely between the outside surfaces of the cornerkey and the inside surfaces of the formed section while preventing thefoam from escaping through the miter joints of the window casement framecomponents to the outside surfaces of the product. A similar method isused to create the window casement sash as well.

The urethane foam fill is injected into the window assembly to serveseveral functions, including: 1) providing permanent adhesion to thecorner key and the roll-formed/extruded composite window components, 2)blocking water seepage into the interior of the window assembly, 3)blocking air flow through any small gaps in the window assembly, and 4)significantly improving the structural integrity of the window casement.

The increased structural integrity and thermal efficiency of thedisclosed invention allows for a wide variety of design profiles. Theframe components can be made of a full range of colors without risk ofthermal instability. In addition, a window frame and sash that isfabricated from the disclosed method can withstand 50 mph wind drivenrain without leakage due to reduced deflections caused by increasedrigidity, which allows weather seals between the window casement frameand sash components to remain in contact.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simple diagram of the roll-forming and extrusion processused to create a first sub-part.

FIG. 2 is a cross-sectional view of the first sub-part after it has beenroll-formed (shown along lines 2--2 of FIG. 1).

FIG. 3 is a cross-sectional view of the first sub-part of FIG. 2 after athin layer of ETP has been extruded over it in predetermined functionalshapes (shown along lines 3--3 of FIG. 1).

FIG. 4 is a simple diagram of the roll-forming and extrusion processused to create a second sub-part that is a counterpart to the firstsub-part.

FIG. 5 is a cross-sectional view of the second sub-part after it hasbeen roll-formed (shown along lines 5--5 of FIG. 1).

FIG. 6 is a cross-sectional view of the second sub-part after a thinlayer of ETP has been extruded over it in predetermined functionalshapes (shown along lines 6--6 of FIG. 4).

FIG. 7 is a simple diagram of the roller assembly station used toconnect the first sub-part and the second sub-part to form a length ofstructural component material.

FIG. 8 is a cross-sectional view of the resultant length of thecomponent material.

FIG. 9 is a cross-sectional view of a fabricated structural windowcomponent of an assembly after urethane foam has been injected withinits hollow interior and allowed to expand and cure.

FIG. 10 is an exploded view of a two-sash casement with common frame andcorner key assembly, with arrows depicting the flow path of the urethanefoam fill as it is injected into the window casement assembly.

FIG. 11 is a top view of the two sash casement with common frame of FIG.10.

FIG. 12 is an exploded view of a sash and corner key assembly, witharrows depicting the flow path of the urethane foam fill as it isinjected into the sash assembly.

FIG. 13 is a perspective view of the hollow corner key of FIGS. 10 and12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to corner keys used in assemblingstructural components to form a structural shape, such as a frame andsash section for a window, door panel, or other building orarchitectural construction. The structural shapes are the subject ofU.S. Application Ser. No. 09/148,516, incorporated herein by reference.The structural components are formed by a process that includes the useof roll-formers 12 which continuously form a first sub-part 14 frompre-treated metal in flat coil stock form, as shown in FIG. 2. Thepreferred metal is aluminum in flat coil stock, although it is knownthat other similar type structural metals could also be used. Directlybehind the roll formers 12 are cross-head extruders 16 which extrude aprofile of one-hundredth to six-hundredths of an inch layer of asynthetic material 18, preferably an Extrudable Thermal Plastic (ETP),to both the outside and inside surfaces of the first sub-part 14, as canbe seen in FIG. 3. An example of an ETP of this nature is GEON, apolyvinyl resin manufactured by the B. F. Goodrich Company.

FIG. 4 is a diagram of a similar process for forming a second sub-part20 that is the counterpart to the first sub-part 14 of FIG. 3. Thesecond sub-part 20 is roll-formed to form the embodiment of FIG. 5, andthen a profile of one-hundredth to six-hundredths of an inch thick layerof ETP 18 is extruded onto the second sub-part 20. It is preferred thatsome areas have thicker layers of ETP applied, as shown in FIG. 6, toimprove the dent resistance of the window frame and/or sash.

With specific reference to FIG. 3, some of the ETP 18 is extruded ontothe first sub-part 14 in a functional shape, such as the "C" shapedpockets 22a,b. The two sub-parts 14 and 20 are then joined together toform a length of structural component material 24, with the "C" shapedpockets 22a,b clipping the first sub-part 14 together with the secondsub-part 20, as seen in FIG. 8. A second function of the "C" shapedpockets 22a,b is that they provide for both a thermal break and a noisebreak within the structural component material 24.

This process of extruding ETP shapes over roll-formed shapes extends thetraditional roll-forming process with the capability of incorporatingadditional functional shapes onto or into the roll-formed component thateither could not be done by roll-forming alone or would be costprohibitive from a roll-form tooling standpoint. Material can be locatedon the interior or exterior of the roll-formed component to enhanceperformance and assembly requirements. It also extends traditional PVCextrusion process by allowing dark colors to be used without risk ofheat deflection. The process has the further advantage of runningbetween four to eight times faster than traditional extruded PVCcomponents. This, combined with utilizing thin roll-forming and ETPmaterials, allows this process to produce components that areapproximately the same manufacturing cost of traditional PVC extrudedcomponents, while incorporating superior mechanical properties.

After the roll-formed/extruded length of structural component material24 leave the roll-coupling station 25 of FIG. 7, they are cut intolineal lengths, approximately sixteen to twenty feet, which are ready tobe fabricated into window/structural components. For purposes ofthewindow frame 26 shown in FIG. 10, the lineal lengths are miter-cut toform window frame components 28.

FIG. 10 depicts a two-sash window frame 26 having a construction thatutilizes four hollow injection-molded corner keys 30, the subject of thepresent invention. Although it is well-known in the art to providewindow frame and sash components with various types of cuts, thepreferred embodiment is illustrated as comprising miter-cut framecomponents 28 and four hollow injection-molded corner keys 30 that serveto join or couple the assembly together. In this particular embodiment,center corner keys 31 are also used. Once assembled, the parts can betemporarily held together via a small fastener (not shown) which passesthrough the frame components 28 into and through the wall of the cornerkey 30. As seen in FIGS. 10 and 12, small holes 34a,b (approximately 3/8inch in diameter) are drilled mid-point on opposite sides of the windowframe 26 (FIG. 10) and window sash 32 (FIG. 12), although it is knownthat the small holes 34a,b could be created anywhere along the exteriorof the window frame 26 and sash 32. Two rubber grommet type devices36a,b are inserted into holes 34a,b, respectively. The first grommet 36ais designed for a filling nozzle (not shown). A two-part urethanedispensing machine (also not shown), capable of injecting a precise shotof one to ten pounds of urethane foam 38 (via the filling nozzle whichis inserted into the first grommet hole 36a) is used to fill theinterior of the window frame 26 (FIG. 10) or sash 32 (FIG. 12). Firstgrommet 36a also functions to keep the urethane foam 38 off of thefinished outer surface of the window frame 26 and sash 32. The secondgrommet 36b acts as a vent plug to allow air to escape from hole 34bduring the filling process, but retains the urethane foam 38 within thehollow window frame 26 (shown in partial view in FIG. 10) and sash 32(shown in partial view in FIG. 12).

The preferred material for the urethane foam 38 is an expandedpolyurethane-urea polymer comprising inter-reacting polymer isocyanateA, polyether polylol based on sucrose and glycerin initiators componentsB, polyester diol or polyol components C, chain-extending glycolcomponents D, silicone surfactant component E, water component F andpolyurethane catalysts. Each component is present in those relativeproportions by weight, as known to one skilled in the art, to produceexpanded rigid polyurethane foam with a density of four pounds per cubicfoot. The water content F can be varied to also give densities rangingfrom 1.5 to 35.0 pounds per cubic foot. A chemical foam such as the onedescribed is manufactured by Azon USA, Inc. under the productdesignation 13 302 A. A similar type foam, also produced by Azon USA,Inc., is sold under the product designation SUF 200 Series Component B.

The foam 38 is forced under pressure to flow through the entire assemblyand expand to fill all of the internal voids of the window frame 26, asshown in FIG. 9. The hollow corner keys 30 are designed to allow theliquid foam 38 to pass through with minimal restriction.

Although the corner key 30 is designed so as to closely fit within theframe components 28, gaps ranging from five one-thousandths of an inchto ten one-thousandths of an inch still exist between the exterior ofthe corner key 30 and the interior of the frame component 28. Thesegaps, which extend along the miter joint area of the structural framecomponent 28, create voids that impede the flow of the urethane foam 38around the miter joint. To overcome this impedance, as best shown inFIG. 13, the key 30 has strategic vent holes 40 molded into its outerwalls to allow the foam 38 to flow around the outside of the corner key30, which locks it to the window frame components 28. In addition, aseries of recesses 42, which are integrated into the injection-moldedcorner key 30, allow the foam 38 to flow freely between the outsidesurfaces of the corner key 30 and the inside surfaces of the windowframe components 28 while preventing the foam 38 from escaping throughthe miter joints of the window frame components 28 to the outsidesurfaces of the product. Further, a secondary groove 46 is molded intothe corner keys 30 at the miter joint area to allow a caulk, or anysimilar type adhesive, to be injected through a hole (not shown) at eachcorner of the window frame 26 and into the secondary groove 46 of thecorner key 30. The addition of the caulk bridges the vinyl andaluminum/steel miter cut edges to increase corrosion resistance incoastal applications.

Once filled with the urethane foam 38, which should take approximatelytwenty seconds for a four-foot by four-foot frame, the window frame 26must sit in a square and flat stable condition until the urethane foam38 cures to a solid. This curing state varies between thirty seconds andthirty minutes, depending on the catalytic reaction built into the foamformulation. After curing is complete, the window frame 26 can befurther processed like any other window frame component, i.e., theattachment of hardware as known to one of ordinary skill in the art. Thewindow sash 32 is manufactured similarly to window frame 26.

The injection of urethane foam 38 into the frame 26 and sash 32 servesthree distinct functions. First, its primary purpose is as a structuralreinforcement. The expansion of the foam 38 throughout the hollowinterior of the frame 26 provides increased resistance to deflection ofthe roll-formed aluminum/steel caused by strong wind or other similarenvironmental conditions. The compressive tensile strength of the foam38 limits the amount of buckling of the frame walls of the framecomponents 28. Should deflection of the aluminum occur, the addition ofthe foam 38 allows for the aluminum to return back to its originalposition, without any damage to the structure of the frame 26.

Consequently, the structural integrity of the frame 26 is significantlyimproved by the urethane foam fill 38. The composite frame component 28(without foam filling 38) would act as a thin-walled column or beam.Generally, the load capacity of such thin-walled sections is limited bya buckling mode of failure. Thin walled sections may buckle under axial,torsion, or bending load. The fundamental reason is that the thin wallsprovide little resistance to lateral deflection.

Buckling of an un-reinforced section would initiate at some smalllocalized imperfection, such as a dent or scratch. Axial, torsion, orbending loads on the section would cause lateral deflection in thevicinity of the defect and subsequently lead to instability and bucklingcollapse of the section. Thus, failure may occur at loads well below theyield limit of the section. The foam fill 38 within the section greatlyreduces the lateral deflections, even if relatively large defects arepresent.

Increased lateral rigidity due to the foam fill 38 greatly reduces thetendency for buckling failure and thereby the load capacity of the framecomponents 28 are substantially increased. In addition, the injectedfoam 38 may fill in gaps between parts such as might occur to slightmismatch or misalignment of mating surfaces. As a result, load transferbetween mating parts is more evenly distributed across the cross sectionof the frame 26. Uniform loading reduces the tendency for bucklingfailure and thus increase the load capacity of the frame components 28.

Secondly, the foam 38 acts as a sealant. As the foam 38 cures, itadheres the various pieces 28 and 30 of the frame 26 together, therebylocking them in position.

Finally, the foam 38 also acts as insulation against the thermaltransfer of heat through the frame components 28. In addition, acombination of the two sub-parts 14 and 20 joined to form the structuralcomponent 24 having both a thermal and noise break, plus the layer ofETP 18 extruded on both the inside and outside surfaces of the twosub-parts 14 and 20, plus the addition of the urethane foam 38 withinthe resultant frame components 28, provides an excellent sound barrier.

For all of these functions, it is desirable to completely fill thespaces in between the corner keys 30 and extruded composite framecomponents 28. As can be seen in FIG. 12, vent holes 40 in the cornerkeys 30 facilitate complete filling of the recessed regions 42 of thecorner keys 30. A particular difficulty of filling the recesses 42, inthe absence of vent holes 40, is that the flow diverges into therecesses 42 immediately following an expansion of the flow (and thus apressure drop in the flow stream) from the main cavity of the cornerkeys 30 into the main cavity of the extruded frame components 28. Thisis followed by a one hundred eighty degree turn into a long narrow flowpath into the recesses 42. The vent holes 40 are more favorably locatedin the narrower (higher pressure) section of flow stream. The holesdiverge at ninety degrees from the main cavity of the corner keys 30 andthen lead into the recesses 42 where the flow diverges in all directionsto fill the adjacent regions. The vent holes 40 may be centrally locatedwithin the recesses 42 and thereby reduce the length of the flow pathwithin the narrow recess 42. Thus, the vent holes 40 solve the abovementioned difficulties in filling the recessed areas 42 of the cornerkeys 30.

A principle advantage of filling the recessed area 42 of the corner keys30 through the vent holes 40 is that it provides the ability to adjustthe flow into the recesses 42 without changing the design of therecesses 42 themselves. The geometry of the recesses 42 may thus bedesigned for optimum functionality in terms of the adhesion and lockingcapability. The flow into the recesses 42 can be separately controlledby the design of the vent holes 40. Flow into the recesses 42 isinfluenced by changing any of the following: the number and location ofthe vent hole(s) 40, the size of the vent hole(s) 40, and the geometryof the vent holes 40 (e.g., round versus rectangular, radius edgesversus sharp edges).

Various features of the invention have been particularly shown anddescribed in connection with the illustrated embodiment of theinvention. However, it must be understood that these particulararrangements merely illustrate, and that the invention is to be givenits fullest interpretation within the terms of the appended claims.

What is claimed is:
 1. A corner key particularly adapted for use inconnecting adjacent mitered hollow frame members in a structural unitcontaining injected foam, said corner key including:a hollow body memberincluding a first leg and a second leg disposed substantiallyperpendicular to said first leg; a flow channel communicating thru saidbody member from said first leg thru said second leg; one or morerecessed portions formed on the exterior surface of said body memberadapted to contain urethane foam; and at least one vent passage disposedbetween said flow channel and said recessed portion to allow limitedflow of the injected foam from said interior of said body member to saidexterior recessed portion.
 2. A corner key in accordance with claim 1including a flow groove defined on the exterior surface of said hollowbody member at the intersection of said first and second legs adapted tocontain a sealant material to seal said corner key to the structuralunit.